Treatment of organic wastewater by a synergic electrocatalysis process with Ti3+ self-doped TiO2 nanotube arrays electrode as both cathode and anode

Electrochemical anodic oxidation (AO) is a promising technology for wastewater treatment due to its strong oxidation property and environmental compatibility. However, it suffers from high energy consumption for pollutants removal due to the side-reactions of hydrogen evolution reaction on cathode and oxygen evolution reaction on anode. Combining electro-Fenton (EF) with AO not only generated •OH for pollutants degradation but also increased current efficiency. This work investigated a synergic electrocatalysis process between EF and AO with Ti3+ self-doped TiO2 nanotube arrays (Ti3+/TNTAs) electrode as both cathode and anode for wastewater treatment. The pseudo-first-order kinetic rate constant of phenol degradation by EF+AO (0.107 min-1) was 9.7 or 6.3 times as much as that of only EF (0.011 min-1) or AO (0.017 min-1) process, respectively. Enhanced pollutants removal of EF+AO could be attributed to the coexistence of •OH oxidation and direct oxidation on Ti3+/TNTAs surface. The COD of secondary effluent of coking wastewater decreased from 159.3 mg L-1 to 47.0 mg L-1 by EF+AO within 120 min with low specific energy consumption (9.5 kWh kg-1 COD-1). This work provided a new insight into design of the energy-efficient synergic electrocatalysis process for refractory pollutants degradation.